JPS5934954B2 - How to coat the inner wall of a furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a furnace consisting of walls usually coated on the inside with a refractory or semi-refractory material.

Maintenance of furnaces for processing abrasive materials at medium or high temperatures, as in the case of vertical furnaces for lime, dolomite, fireclay, etc., but also horizontal rotary furnaces, e.g. for cement, and especially in blast furnaces. due to the extreme stress they are subjected to,
Frequent refractory lining repairs are required.

Particularly in the areas of wear, these linings can be damaged down to the shell within a very short period of time, which period is in each case shorter than the service life of the remaining furnace parts.

In order to thus avoid extremely frequent and complete repairs of these linings, a number of repair methods have been proposed.

In the first method, the charge is completely or partially evacuated and a suitable refractory concrete is sprayed by air pressure onto the furnace walls from the inside of the furnace.

Disadvantages of such methods are interruptions in the operation of the equipment, extra consumption and handling of processing materials, and the difficulty in carrying out such operations.

The second method consists in spraying the amorphous refractory mixture mechanically or pneumatically or by other methods from outside the furnace through a conduit made for this purpose.

It is desired that this material adhered to the wall, together with the contents, form a mass to a certain thickness and protect the wall for a period of time.

Generally, the duration of these deposits is short, due to the low resistance of the adhesive forces to the sliding forces due to the movement of the charge acting on the non-uniform protrusions obtained by this method. , can be easily explained.

More recently, certain methods have been proposed to partially overcome the aforementioned drawbacks.

This is accomplished by charging a relatively fluid material into the furnace, as described above, and spraying it against the walls using appropriate equipment.

Although such solutions improved the quality of the connection with the wall,
This does not eliminate the disadvantage of discharging a portion of the charge, but only leads to an unstable distribution of the material to be treated.

Furthermore, when using highly fluid mixtures, rapid curing is necessary, especially when the thermal potential is low.

The aim of the invention is to overcome the drawbacks of the various known methods mentioned above.

The invention provides a maintenance and repair method which also allows for the regeneration of the refractory lining of a furnace, by which the wall to be treated is first formed with a temporary continuous surface with the charge. A first material suitable for this purpose is injected from the outside of the furnace through a conduit in the furnace wall, after which sufficient time has elapsed to form the final lining between this injected layer and the furnace wall. A second substance, which is suitable and serves as a protection substance against wear of the refractory lining, is introduced under pressure.

In the second stage, the compressibility of the charge is exploited;
The lining material sufficiently pushes the charge away from the wall,
The voids thus formed will be filled.

The invention will now be described in more detail with reference to the accompanying drawings, which are shown by way of example and relate to a process according to the invention.

This drawing shows an element of a furnace wall, which may be, for example, a blast furnace, with a refractory lining 2 applied to the shell 1, which lining is completely covered as shown in zone 2a. It may have disappeared.

A conduit 3 is formed in this wall, allowing the injection of treatment substances.

On the inner surface of the furnace there is a charge 4, the nature of which, of course, depends on the application of the furnace.

According to the invention, the procedure includes protecting and maintaining the furnace lining;
Or depending on the purpose of reconstruction, as shown below.

First, the first substance 5 is injected from outside the furnace through a conduit 3 provided in the furnace wall by suitable mechanical or pneumatic or other equipment.

During this injection, the voids in the charge near the wall are gradually filled, which serve as a framework for the inner surface of the furnace when the final lining material is installed.

This first material may, of course, be of a wide variety of compositions depending on the requirements of the application.

In order to take advantage of the temperature of hydraulic materials, minerals, organic materials, clayey materials or other charges, it is preferred to consist of a thermosetting binder.

This composition is usually inexpensive as it is neither required nor desirable to have highly mechanical properties.

By way of example (but not limitation), a hydraulic mortar having the following composition can be applied using a pneumatic sprayer equipped with a nozzle 6 as shown in the figure.

i.e. 600-900 kg of granules (particle size 0.2 mm) and 100-400 kg of Portland or alumina cement per ton of mixture.
A composition comprising.

The above-mentioned granules can be widely used with various properties, and fireclay, expanded clay, silica sand, crushed brick waste, etc. are selected depending on local conditions and difficulty in obtaining them. In the case of a blast furnace, the choice may be made of granulated slag, ore or briquettes.

In each case, the particle size of the mixture is selected so that the mixture is easily transported pneumatically and has a sufficiently dense structure after curing.

Furthermore, pneumatic atomization has two significant advantages.

First, it is possible to deliver a substance with a very low liquid content, in other words, a substance containing the minimum amount of liquid necessary for curing, to a sufficient distance from the point of introduction.

Secondly, at least if the charge contains combustible elements such as coke, the introduced air can cause localized combustion to generate considerable heat, facilitating subsequent operations. .

Insertion under pressure is required once sufficient time has elapsed to ensure that the interface area between the furnace wall and the charge has received sufficient temperature and/or that the injected material has sufficiently hardened. A suitable injection of the second substance 7 can be performed.

This second substance is preferably a mortar which has a relatively high viscosity, hardens at a temperature specific to the local conditions, and has as high an adhesion to the oven wall as possible.

Under the influence of a pressure of the order of 2 to 10 bar by means of a dosing device, for example a pump, this mortar slides between the wall and the coated charge and is pushed into place over a distance corresponding to the thickness of the mortar injected. Only push the charge away.

This distance is a function of the amount of mortar introduced by each conduit 3.

As long as this mortar is a fluid, the above-mentioned applied pressure is sufficient to move the charge coated with layer 5 over the required distance under an effective pressure in the furnace that does not impose any more stress on the shell than during normal operation. This is enough to move only

A charge with voids and poor compactness is compressible (at most a few percent) as required by the method of the invention.

).

By way of example, the final mortar used may have the following composition:

Mineral component (refractory) 40-75% by weight Ceramic inter (clay + additives) 5-30% by weight Carbonaceous component (tar + pitch) 10-30% by weight Organic binder (resin) 10-40% by weight Mineral The quality components can be formed by refractories or semi-refractories, especially fireclays (clays with high or very high alumina content), corundum, silica, silicon carbide, calcined anthracite, graphite, magnesia, etc.

The resin is preferably a phenol type. Mortars of this type have the advantage of being moderately priced and that the viscosity can be adjusted by varying the ratio of tar to resin in the charge to suit local conditions.

Furthermore, the curing time can be shortened by adding polymerization accelerators to the resin, and the final ceramic bond can be adjusted by introducing ceramic formers.

According to the method of the invention described above, by carrying out each of the injection operations described above, it is possible to achieve a substantially even and uniform distribution of the final mortar on the inner surface of the furnace thus treated.

The area of the area coated with a certain thickness, which varies by adjusting various factors, inter alia by the amount of substance injected, can be more than 5 square meters on a plane considered to be approximately flat.

However, in practice it is interesting to treat small sections by bringing the conduits 3 as close to each other as possible.

In this case, you can check whether the final mortar has reached a sufficient depth by seeing the mortar in the conduit next to the conduit you are using.

This ease of access also makes it possible to treat surfaces with protrusions, such as cooling boxes, for example.

Preferably, the aforementioned layer with a thickness of 5 to 10 CIrL adheres to the treated wall, the performance of which in use being measured by the wear rate, satisfactorily meets the requirements in practice, especially the overall thickness. The condition is good after some or all of them are formed into ceramic.

This excellent feature is due to the fact that the final mortar sticks firmly to the wall due to the large pressure during installation.

It will be appreciated that this approach is useful for all furnaces containing a charge to be treated.

Thus, as a non-limiting example, this method can also be applied to horizontal rotary furnaces of the cement kiln type, by carefully continuing this operation to each part of the furnace perimeter that is covered by the charge when the furnace is stopped. It can be applied if it is carried out.

It goes without saying that many modifications to the above-mentioned system are possible, depending on the refractory lining of the furnace, the nature of the charge to be treated, and the temperatures utilized in the various zones and locations of the furnace.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the vicinity of the furnace wall to show the condition of the inner surface of the furnace wall to which the method of the present invention is applied. The symbols in the figure represent the following: 1... Iron skin, 2... Fireproof lining,
3... Conduit, 4... Charge, 5...
...First substance, 6... Nozzle, 7...
...Second substance.

Claims (1)

[Scope of Claims] 1. A method for maintaining, repairing or regenerating the refractory lining of a furnace wall by injecting a substance for protecting the refractory lining against wear between the furnace wall and the contents in the furnace, the method comprising: injecting a first substance from outside the furnace through a conduit provided in the furnace wall to form an intermediate layer between the charge and the protective substance;
Maintenance of the refractory lining of the furnace wall, characterized in that, after a sufficient period of time has passed, a second substance, which is a protective substance, is injected through the conduit between the intermediate layer and the furnace wall; Method of repair or refurbishment. 2. The method according to claim 1, wherein the second substance is a mortar that fills a gap between the furnace wall and the furnace contents and is integrated with the furnace contents. Method. 3. The method according to claim 2, wherein the mortar is a mortar consisting of a hydraulic cement binder and various particles of an inert refractory material. 4. The second substance has strong adhesion to the furnace wall and hardenability at low temperatures, and when heated, forms an organic, chemical or ceramic bond, so that it can withstand high temperatures and be treated. The method according to claim 1, characterized in that the mortar is a mortar in which refractory particles of a suitable mortar are strongly bonded to the surface. 5. The method according to claim 4, wherein the mortar has the composition shown below. Mineral component (refractory) 40-75% by weight Ceramic powder (clay + additives) 5-30% by weight Carbonaceous component (tar + pitch) 10-30% by weight Organic binder (resin) 10-40% by weight %